I'm sorry to say this, but a 30-day water fast just sounds irresponsible to me. The ultimate goal of all this fat loss that people are trying to achieve on this forum is to get down to a weight where their health is no longer threatened by looming dangers of diabetes, heart disease, arthritis, and everything that comes with overweight/obesity. Which means... you shouldn't trade away your health to get there.

While a 24-hour fast sounds reasonable to me (especially when giving the body a chance to recover from a weekend of brutal eating), I'd imagine 30 days causes some serious nutritional depletion in addition to a high caloric deficit. I wouldn't recommend it at all.

Disclaimer: I'm not professionally qualified to make any formal recommendations. I've just done my homework and I'm my own guinea pig. All of my data, unless otherwise cited, comes from a sample size of n=1 (me).